The invention relates to railroad cars, especially the trucks or bogies used to support the railroad cars as they move along a fixed trackway. More particularly, the invention relates to multi-axle trucks which have two or more axles.
U.S. Pat. No. 3,670,660 discloses a dual axle railroad car truck which is manufactured and sold by National Castings Incorporated of Chicago, Ill. under the trademark SWING MOTION. This particular truck has a pair of parallel twin axles which are carried by a pair of side frames, each of which has a pair of inverted U-shaped pedestals at its opposing ends. The side frames are in vertical, parallel planes, when the truck is in a normally rest position on a horizontal surface or trackway. The SWING MOTION truck has a transversely extending bolster which is swing mounted to the side frames by means of, 1) a rocker seat arrangement, and 2) a suspension and snubbing mechanism which cushions, isolates and dampens undesirable vibrations or motion imparted to the wheels, axles and side frames during operation of the truck, i.e. the side frames can swing or lean out of the aforementioned vertical planes of the side frames during operation of the truck. The opposing ends of the twin axles are held captive in bearings which are carried by adjacent pedestals, so that as the side frames swing or lean, the axles correspondingly move in axial directions or laterally of the longitudinal axis of an attached railroad car or a trackway along which the car is moving. Such lateral movement of the axles helps the truck to better negotiate lateral misalignments of adjacent rails of the trackway and sharp curves in the trackway. Other than manufacturing clearances between the bearing mountings and pedestals, no other lateral or longitudinal motion is provided for the axles of a SWING MOTION truck.
U.S. Pat. No. 3,394,662 discloses a single axle railroad car truck which is manufactured and sold by the above company under the trademark UNITRUCK. This truck has a pair of side frames which are essentially pedestals, as used on the SWING MOTION truck. A saddle is swing mounted in substantially coplanar relation generally within each pedestal by means of, 1) a pedestal rocker seat-adapter arrangement, and 2) a suspension and snubbing mechanism, similar to that used in the SWING MOTION truck. Each of the opposing ends of the single axle is, likewise, held captive in a bearing carried by the adjacent saddle, so that as the saddles swing, lean or tilt out of the plane of the pedestals during operation of the truck, the single axle will correspondingly move axially or laterally of the railroad car and trackway. The pedestals loosely guide the single axle, bearings, rocker seat-adapter arrangements and saddle assemblies in a floating manner, so as to allow and limit the swinging or tilting of the saddles and consequent lateral motion of the axle. Moreover, the pedestals allow and limit a predetermined and controlled amount of longitudinal motion of the saddles and consequent longitudinal movement of the axle to facilitate passive steering of the axle. The technology of the '662 patent has been limited solely to single axle railroad car trucks which are used, for example, on unit trains or railroad cars which employ only two axles.
Railroad cars built today are expected to carry bigger and heavier loads than ever before. For example, railroad cars are designed to carry truck trailers and packaged containers. As a result, railroad cars are made bigger, especially longer, and sometimes with heavy structural bodies, thereby creating new problems for those associated with the railroad industry. For example, because of the increased length of newer railroad cars, the railroad car trucks are now spaced farther apart to where lateral movement and passive steering of the truck axles has become critical to the safe negotiation of small radius curves which presented no problems for the shorter cars built in the past. Heavier loading of railroad cars causes two problems; namely, the need for greater support and better weight distribution on the axles, so as not to damage or destroy the trackway or underlying road bed of the trackway. To meet the first of these two problems, conventional dual axle trucks have been beefed up to increase their strength, and longer, stronger tri-axle trucks are being built to support and better distribute the heavier loads to the trackway and track bed. The invention is in an improved multi-axle truck which is designed to more easily accommodate these larger railroad cars and better negotiate the shorter radius curves of existing railroad trackways.
Briefly stated, the invention is in a multi-axle railroad car truck wherein one or more bolsters are rigidly secured between a pair of side frames which carry two or more axle and wheel assemblies. Moreover, each of the axles is designed to move laterally independently of the other axles from 1" to 11/4", measured in either of two opposing directions from a vertical plane midway between the side frames, when the truck is in a normal rest position on a horizontal surface or trackway, or an overall distance of from 2" to 21/2" as compared to the axles of most conventional trucks which am capable of moving laterally only about 1/8" in either direction from such vertical plane. Further, each of the axles is permitted a controlled longitudinal motion which effectively increases passive steering of the axles.
Another aspect of the invention is in the provision of each of the axle ends with its own, independent suspension and motion dampening or snubbing mechanism, contrary to the majority of existing dual or tri-axle railroad car trucks which are provided with a single suspension and motion dampening mechanism only at each end of the bolster of the railroad car truck.
It can be appreciated by those skilled in the art that such lateral and longitudinal relative movement between the axles and pedestals makes it much easier for the truck to adjust to variations in the trackway or small radius curves which, otherwise, may be perilous to negotiate without derailment.